Babies with microcephaly have abnormally small heads and brains. The discovery may be the first step in finding ways to prevent the birth defect, the researchers said.

The Zika virus contains 10 proteins, but only two -- called NS4A and NS4B -- are linked to microcephaly, according to the researchers.

The study, from a team led by University of Southern California scientists, was published Aug. 11 in the journal Cell Stem Cell.

"We now know the molecular pathway, so we made the first big step toward target therapy for Zika-induced microcephaly," corresponding author Jae Jung said in a university news release.

"Years from now, one shot or a series of shots could target the proteins NS4A and NS4B or their collaborators," said Jung, chairman of USC's department of molecular microbiology and immunology.

The USC researchers said they're trying to learn more about NS4A and NS4B through mouse studies and brain organoids, which are artificially grown tissues resembling the brain.

"It is important to remember that not every pregnant woman infected with Zika virus gives birth to a baby with microcephaly. Nevertheless, we are trying to develop a cure for that percentage that does get Zika-related microcephaly," said study corresponding co-author Zhen Zhao.

Zhao is an assistant professor of research physiology and biophysics at USC.